1. Field Of The Invention
This invention relates to the preparation of organic carbonates. More particularly it relates to urea cosolvents for the preparation of dimethyl carbonate (DMC). DMC may be used as a gasoline extender and octane enhancer, as an organic solvent or as a reactant in place of phosgene in the preparation of isocyanates, polycarbonates, and various agricultural and pharmaceutical intermediates.
Dimethyl carbonate (DMC) may be prepared by the reaction of methanol with carbon monoxide and oxygen in the presence of a catalyst system. Those skilled in the art, constantly seek new or improved catalysts or additives for such catalysts to lower costs, to improve reaction conditions, the yield and rate of production, and to facilitate separation of reactants, products, and catalysts.
Thus, it is an object of this invention to provide an improved method of preparing dimethyl carbonate, lower the cost of the process, substantially increase the yield and rate of production of dimethyl carbonate, and ease the separation of DMC and water from the catalyst system.
2. Disclosure Statement
U.S. Pat. No. 3,114,762 discloses as catalysts, metal salts including chlorides and bromides of platinum and palladium plus an oxidizing agent such as iron or copper salts having the same anion.
U.S. Pat. No. 4,638,076 discloses use of phosphoramide additives for the preparation of organic carbonates.
U.S. Pat. No. 4,636,576 discloses use of cyclic amide additives for the preparation of organic carbonates.
U.S. Pat. No. 3,227,740 discloses as a catalyst, a mercuric halide or a carboxylate.
Saegusa, et.al., J. Org. Chem., 35,2976-2978 (1970) discloses the reaction of CO with copper alkoxides including the dimethoxide, the diallyloxide, the chloride methoxide and the acetylacetonate methoxide.
Romano, et.al., IEC Prod. Res. Deve. 19, 396-403 (1980) discloses as a catalyst, cuprous chloride/cupric chloride methoxide.
U.S. Pat. No. 4,218,391 discloses as catalysts, salts of metals of Group IB, IIB and VIII, preferably monovalent copper such as cuprous bromide, chloride or perchlorate.
U.S. Pat. No. 4,318,862 discloses as catalysts, salts of metals of Groups IB, IIB or VIII, typically a copper salt such as CuCl.
U.S. Pat. No. 3,846,468 discloses as catalysts, cuprous chloride complexes with an organic ligand such as pyridine, dipyridyl, imidazole, phenanthroline, alkyl, or aryl phosphines, dimethyl sulfoxide, dimethyl formamide, quinuclidine, acetonitrile, benzonitrile, malonitrile, succinodinitrile, or adiponitrile.
U.S. Pat. No. 3,980,690 discloses as a catalyst, a complex of copper chloride and poly-4-vinylpyridine.
Rivetti et al, J. Organometallic Chem, 174 (1979) 221-226 discloses as catalysts, palladium (II) complexes in the presence of ligandp and added bases. Alkyl phosphines are said to inhibit carbonylation almost completely. The presence of tertiary amines enhances the formation of dimethyl carbonate.
U.S. Pat. No. 4,370,275 discloses catalyst compositions containing copper, chemically bonded oxygen, and halogen and a nitrogen base. A typical catalyst contains CuO or Cu(OCl).sub.2 and n-butylamine inter alia. Preferred combinations include: CuCO.sub.3, Cu(OH).sub.2; CuCl.sub.2 and pyridine hydrochloride etc.
U.S. Pat. No. 4,131,521 discloses an electrochemical process utilizing a non-fluoride halide-containing electrolyte.
U.S. Pat. No. 4,113,762 discloses as a catalyst, a complex of copper (as CuCl) with VCl.sub.3, CrCl.sub.3, FeCl.sub.3, CoCl.sub.2, AlCl.sub.3, or SiCl.sub.4.
U.S. Pat. No., 4,361,519 discloses as catalyst (i) a Bronsted base such as a quaternary ammonium, phosphonium, or sulfonium compound or an alkoxide or hydroxide of alkali metal or alkaline earth metal or a salt of a strong base and a weak acid or amines etc. plus (ii) a Group VIII B element Ru, Rh, Pd, Os, Ir or Pt plus (iii) oxygen plus (IV) a redox catalyst such as a Mn or Co containing catalyst. A typical system includes (i) a pentamethylpiperidine, (ii) PdBr.sub.2 and (iii) pyridine adduct of salicylaldehyde - ethylene diamine Co (II) complex.
European Patent 0,071,286 discloses as a catalyst a copper compound such as a halide (in the presence of an amine) plus a sulphone such as dimethyl sulphone or sulfolane.